Stern construction for icebreaking vessels

ABSTRACT

A construction for the stern of an icebreaking vessel wherein the stern is constructed and arranged to have a shape such that the vessel as it backs into its own broken channel filled with previously broken ice, effectively will shovel the ice pieces up and to the sides of the vessel, thereby clearing the channel so as to facilitate backing and simultaneously keep the ice away from the vessel&#39;&#39;s screw(s).

United States Patent Gray Sept. 12, 1972 [54] STERN CONSTRUCTION FOR998,278 7/1911 Clifford ..l14/57 X ICEBREAKING VESSELS 3,521,590 7/1970German et al. ..1 14/41 [72] lnvmon wllham Primary Examiner-Trygve M.Blix Asslgneer Essn Research and Engineering, Attorney-Manahan & Wohlersand F. Donald Paris Company 22 Filed: Dec.2l, 1910 [57] ABSTRACT Aconstruction for the stern of an icebreaking vessel [21] Appl' l00l71wherein the stem is constructed and arranged to have a shape such thatthe vessel as it backs into its own [52] Cl ..1l4/41 broken channelfilled with previously broken ice, ef- [51] Int. Cl. ..B63b 35/08fectively will shovel the ice pieces up and to the sides [58] Field ofSearch 114/4042, 57 of the vessel, thereby clearing the channel so as tofacilitate backing and simultaneously keep the ice [56] References Citedaway from the vessels screw(s).

. UNITED STATES PATENTS 6 Claims, 5

PATENTEDsEP 12 1912 SHEET 10F 2- Y 4 M m N M m WM MO Q w WJ/ Y B STERNCONSTRUCTION FOR ICEBREAKING VESSELS BACKGROUND on THE INVENTION Withthe relatively recent discovery of vast resources, such as oil, in suchinaccessible areas as the frozen north slope of Alaska, there exists avery urgent need for providing a suitable means for transporting theseresources through remotely situated areas to commercially desirablemarket areas, as typified by the heavily commercialized East Coast ofthe United States and its various population centers. To transport theseresources in the most economical manner, serious consideration has beengiven to moving the resources through the heavily ice-laden passages inthe Arctic, with the hope that these passages could be opened ascommercial year-round trade routes. Consequently, various designs andconstructions for icebreaking ships that would be sufficiently large andpowerful to be able to operate in these ice-infested waters onayear-round basis have been investigated. One such ship constructionthat appears capable of obtaining the foregoing results incorporates astern constructed and arranged in accordance with the present invention.Despite the various obstacles, it is generally agreed and has been shown.from an operational viewpoint that a ship can be constructed andoperated successfully in the ice. Although it has been shown to solvethe problem of the ship breaking the ice when traveling in a forwarddirection, this still leaves the problem of providing a suitable sternconstruction to readily allow the ship to back into its own brokenchannel filled with the previously broken ice while preventing the samebroken pieces of ice from damaging the ships screws. Further, byproviding a ship that easily can back into its own broken channel ofice, this substantially contributes to the efficiency of the ship whenramming ahead in ice thicker than can be continuously broken and alsoprovides a significant reduction in the backing power required.

DESCRIPTION OF THE PRIOR ART Known stern constructions for icebreakers,generally have been characterized by section shapes sloping SUMMARY OFTHE INVENTION The present invention relates to icebreaking ships, andmore particularly to an icebreaking ship having a novel and improvedstern construction.

In accordance with the present invention there is provided anicebreaking ship having a stern construction for enabling ships to breakice and to allow the ship, when backing into its own broken channelfilled with previously broken ice, to shovel the ice pieces up and tothe sides of the ship thereby clearing the channel so as to facilitatebacking and simultaneously to keep the ice away from the ships screws.According to the present invention, the longitudinal sections andprofiles of the stern slop downwardly and aft in the vicinity of thein-ice-operating or load waterline to a distance sufficiently below thatwaterline so that it is below the level of the floating pieces of brokenice. By designing a ship to have a stern shape as disclosed herein,there is provided means whereby the stern can shovel pieces of ice upand to the sides as the ship proceeds astem in a previously brokenchannel so that the channel is cleared to facilitate backing. Further,this type of stem construction provides substantially improvedprotection to the propellers and rudders while the ship is backing andprovides additional protection to the screws and rudders while movingahead from any ice that may be present at the sides of the brokenchannel. The results obtained by utilizing a stern construction inaccordance with the present invention contributes greatly to theefficiency of an icebreaking ship when ramming and further, provides areduction in the required backing power in comparison to previouslyknown prior art icebreakers having conventional shaped stems.

Accordingly, it is a primary object of the present invention to providea novel and improved icebreaking ship having a stern shape that willresult in facilitating the backing of the ship into its own brokenchannel filled with previously broken ice.

Another object of the present invention is to provide a novel andimproved icebreaking ship wherein the stem is capable of clearing achannel as the ship moves astern and providing protection for the shipscomponents located at the stern.

Another object of the present invention is to provide a novel andimproved icebreaking ship having a stern shape wherein the hull formingthe stern slopes down and aft in the vicinity of the waterline to adistance below the waterline sufficient to enable the stern to shovelthe broken pieces of ice up to the sides of the ship as the shipproceeds the stern in its previously broken channel.

A further object of this invention is to provide a novel and improvedstern shape for an icebreakingship which improves the ramming efficiencyof an icebreaker and provides for a reduction in the required backingpower thereof.

Having in mind the above and other objects that will be evident from anunderstanding of this disclosure, the invention comprises theconstruction and arrangements as illustrated in the presently preferredembodiment of the invention which is hereinafter set forth in suchdetail as to enable those skilled in the art readily to understand thefunction, operation, construction and advantages of it when read inconjunction with the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic outline of thetop plan view of an icebreaking ship incorpoating the novel and improvedstem shape of the present invention;

FIG. 2 is an enlarged perspective view of the stern constructed andarranged in accordance with the teachings of the present invention;

FIG. 3 is a side elevation view of the stern of FIG. 1;

FIG. 4 is a half breadth view of the stern of FIG. 1; and

FIG. 5 is a body view of the stern of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Having reference to thedrawings, FIGS. 1 through 5 illustrate in detail a preferred embodimentof the present invention. InFIG. 1 the novel and improved sternconstructed in accordance with the teachings of the present invention isshown as incorporated in an icebreaking ship 11 having a bow portion 12,which typically may be constructed and arranged so that the ships beam,that is, the widest part of the load waterline, is situated in the bowof the ship as illustrated in FIG. 1, references being made to copendingU.S. Pat. Application Ser. No. 48,326 (Case RM-590), filed June 22,1970, for specific details regarding the bow construction. Although thenovel stern of the present invention has been disclosed incorporated-ina ship having a bowconstruction as disclosed in the aforementionedpatent application, it is to be understood that this stern would besuitable for use with various other designs for icebreaking shipsincluding the absence of a wide beam bow..

As best illustrated in FIG. 2 the stern, generally designated 13,comprises concave-like hull sides 14 and 15 which slope down from thedeck 16 and extend outwardly a distance below the load orin-ice-operating waterline (LWL), which typically may be 80 feet asindicated in FIGS. 3 and 5, terminating at a distance sufficiently belowthe load waterline, for example, 60 foot, so that the outwardlyextending portion of the stem is below the level of the floating piecesof broken ice in the channel. The outward downwardly sloping nature ofthe hull in the vicinity of the stern provides for a shape whicheffectively is shovel-like in configuration so that the stern is capableof shoveling pieces of ice up onto its hull sides 14, 15 and thence ontoadjacent unbroken ice as the'ship proceeds-astern in its previouslybroken channel thereby clearing the channel and facilitating backing.Further, as is apparent from thedrawings, the stern shape according tothe present invention provides protection for the conventionallyarranged propellers 17 and l8,'as well as the rudders 19 and 20 whilethe ship is backing and also provides additional protection for thepropellers and the rudders from any ice that may be present at the sidesof the broken channel while the ship proceeds in a forward direction.Since the stern slope terminates below the level of the floating piecesof broken ice, any of the broken ice that may come in contact with theships hull in the vicinity of the stern will be caused to be scooped upand thrown laterally outward of the ships sides 14, 15.

The actual shape and construction of the stern shown in FIG. 1 isillustrated in the usual manner in FIGS. 3, 4, and. 5 by passing aplurality of horizontal and vertical planes at spaced waterlines (WL)and stations, respectively, on the ship and plotting the resulting lineson the coordinate systems as shown. FIG. 3 shows as side elevation ofthe stern portion of the ship of FIG. 1, that is, the fore and aftcurvature from the stern toward the bow of the ships deck as shown inside elevation. The base line coordinates define the stations at whichvertical cuts of the ship are taken including a zero reference line AP(aft perpendicular). Although normally 2] (including the zero station)stations are employed, only those necessary to fully disclose the shipsstern in a clear manner are shown. The vertical coordinates definewaterlines (WL) (feet) taken at different elevations of the ship. Thestem lines (20, 40, .etc.) shown in FIG. 4 illustrate a half-breadthplan view of the stern portion of the ship, while the stern lines inFIG. 5 illustrate a body plan of the sterns shape at various stationsalong the base line. Since the stem is symmetrical about its centerline(CL) only one-half of the stern lines are illustrated in each instance.

Typical lines of a preferred embodiment of a stern constructed andarranged in accordance with the present invention are illustrated inFIGS. 3 through 5. Thus, as shown in these figures, the hull in thevicinity of the stern begins to slopedownwardly and outward of the shipssides at the deck or 100 foot waterline and effectively has a concaveconfiguration such that the slope of the sides approaches asubstantially horizontal plane, that is, the slope decreases as thesides extend .outward from the deck toward their point of termination,so as to form a construction that will enable the stem to shove] thepieces of broken ic'e up onto the sides of the ship as it proceedsastern. The sloping stern sides may terminate, for example, at the 60foot waterline which, as illustrated, is well below the load orinice-operating waterline, which occurs at foot. At the terminatingpoint or the 60 foot waterline, the hull portion of the ship below thatpoint comprises a substantially conventional configuration. Although thestern lines illustrated in FIG. 3 have a generally smooth continuouscurvature, it also is within the scope of this invention to employstraight sections (as indicated by 20A and 35A in broken lines) tocomprise the required shape.

As shown in FIGS. 3 to 5, the preferred embodiment of the heretoforedescribed stern shape extends aft from between Stations 8% and 9 /2 tothe rearmost point on the ship. As illustrated, the lateral outwardextension of the ships sides at the stern extends substantially to, butjust short of the 80 foot waterline, but preferably the stern sidesextend laterally to a waterline substantially 60 to 80 per cent ofloaded draft.

Various alterations of the structure herein disclosed will suggestthemselves to those skilled in the art. The present disclosure setsforth a preferred embodiment of the invention which is for the'purposeof illustration only and is not to be construed as a limitation of theinvention. All modifications of the invention which employ the novelfeatures herein disclosed are intended to be included in the scope ofthe appended claims.

Having thus set forth the nature of the invention, what is claimedherein is:

1. An icebreaking ship having a main deck, a load waterline WL, and ahull including a stern portion of symmetrical shape about thelongitudinal center-line of said ship, said stern portion having lateraland rear sides of substantially concavelike configuration, said sidesterminating in a common plane disposed parallel to and locatedvertically below said main deck, said sides constructed and arranged toslope downward and outward from said deck and terminating outboard ofsaid stem at a predetermined distance below said load waterline WL,whereby said ship, when backing in its own broken channel filled withpreviously broken ice, is adapted to shovel the ice pieces up anddispose them laterally of the sides of the ship.

2. A hull construction according claim 1 wherein said stern sides extendlongitudinally between a Station 8% and the rearward most point of saidship.

3. A hull construction according to claim 1 wherein the slope of saidsides decreases as said side approach their termination point below saidload waterline WL.

4. A hull construction according to claim 1 wherein said stern sidesextend longitudinally between a Station 8% and the rearward most pointof said ship and extend laterally outward of said ship terminating at awaterline substantially 60 to per cent of loaded draft.

5. A hull construction according to claim 1 wherein said sides terminatein a substantially continuous curvature as seen in horizontal section atthe waterline defining the tennination of said sides.

6. A hull construction according to claim 1 wherein said stern portionis constructed and arranged to pro tect any propellers and ruddersassociated with said ship from damage when said ship is proceeding inthe aft direction, as well as from any ice that may be present at thesides of the broken channel in which said ship is preceeding in aforward direction.

1. An icebreaking ship having a main deck, a load waterline WL, and ahull including a stern portion of symmetrical shape about thelongitudinal center-line of said ship, said stern portion having lateraland rear sides of substantially concave-like configuration, said sidesterminating in a common plane disposed parallel to and locatedvertically below said main deck, said sides constructed and arranged toslope downward and outward from said deck and terminating outboard ofsaid stern at a predetermined distance below said load waterline WL,whereby said ship, when backing in its own broken channel filled withpreviously broken ice, is adapted to shovel the ice pieces up anddispose them laterally of the sides of the ship.
 2. A hull constructionaccording claim 1 wherein said stern sides extend longitudinally betweena Station 8 1/2 and the rearward most point of said ship.
 3. A hullconstruction according to claim 1 wherein the slope of said sidesdecreases as said side approach their termination point below said loadwaterline WL.
 4. A hull construction according to claim 1 wherein saidstern sides extend longitudinally between a Station 8 1/2 and therearward most point of said ship and extend laterally outward of saidship terminating at a waterline substantially 60 to 80 per cent ofloaded draft.
 5. A hull construction according to claim 1 wherein saidsides terminate in a substantially continuous curvature as seen inhorizontal section at the waterline defining the termination of saidsides.
 6. A hull construction according to claim 1 wherein said sternportion is constructed and arranged to protect any propellers andrudders associated with said ship from damage when said ship isproceeding in the aft direction, as well as from any ice that may bepresent at the sides of the broken channel in which said ship ispreceeding in a forward direction.